1. Field of the Invention
The present invention relates to an image processing technique, and more particularly, to a method and apparatus for generating visual effects.
2. Description of the Prior Art
As conventional analog video broadcasting is transforming into digital video broadcasting (DVB), digital television becomes more and more popular. In general, the interaction between the digital TV and users is achieved through dialogue blocks or an on-screen display (OSD) shown on the screen. For highlighting an item or a button that been selected by the user, the most common means in the prior art is to change the visual effects of the selected item or button so as to distinguish the selected item or button from other items or buttons. For example, the original color of the selected item can be replaced with another color to emphasize the item.
In the conventional digital television displaying technique, the selected item is displayed on a layer, and a mask graphic object is created on a layer above the layer to which the selected item belongs. The mask graphic object is allocated in a location with respect to the selected item. A video mixer/blender is then employed to mix data of different layers into a composed image. As a result, the mask graphic object covers the selected item in the composed image so that the user senses the visual effect change of the selected item.
In conventional technique, each layer of the digital television requires a corresponding layer processing circuit, which is a complex and costly component. Therefore, the number of layers of the conventional digital television is limited. As mentioned above, the convention art requires at least two layer processing circuits to change the visual effects of a specific block. Obviously, system resources are wasted and hardware costs are increased in the conventional art.